The invention relates to an artificial kidney and, more in particular, an artificial kidney that is suitable for gradual, and at least semi-continuous, blood treatment of preferably ambulant patients.
Patients with a defective kidney function require frequent blood dialysis. During such dialysis blood is taken from the patients body for removal of uremic metabolites (N-containing protein waste products: e.g. urea and creatinine), electrolytes, waste products, accumulative substances, toxic substances, and redundant liquid, while salt concentrations are adjusted. At the same time the blood that is being returned to the patient's body needs to remain in possession of its majority of useful substances originally contained therein. There are generally two dialysis methods in common use: haemo-dialysis and peritoneal-dialysis. Patients treated with haemo-dialysis are required to visit a hospital or dialysis centre typically two or three times a week, where treatment takes typically about from 3 up to 4 hours. During treatment the patient is confined to the static location of the dialysis equipment, which causes severe discomfort to such kidney patients. Patients that can be treated by peritoneal-dialysis have their abdomen cavity rinsed typically 4 to 5 times a day with a special rinsing fluid via a catheter in the abdomen partition. Peritoneal-dialyses has the advantage that it can be performed at the patient's home, but it still requires the patient to be regularly checked in a hospital. These known methods of dialysis are intermittent and represent little more than a bad substitute for a healthy person's kidney which functions continuously for 24 hours and 7 days a week. Patients with deteriorating renal functions and chronic kidney failure thus typically suffer from chronic uremic toxicity. It should therefore not come as a surprise that in spite of the availability of dialysis, kidney patients are generally unhealthier, are continuously feeling tired and experience many side effects, such as heart and vascular diseases, diabetes, tingling, impotencies, as well as a generally shortened life expectancy. Moreover kidney patients experience much impact on their social life and psychological wellbeing, and more often than not have become unable to participate in, or contribute to economical processes. Increasing the speed of these known static dialysis processes is not an option, because removal, and return, of blood from and to a patient's body at a too rapid rate would result in cardiovascular problems. Dialysis even at the present ‘slow’ rate still frequently results in side-effects in the patient. One commonly experienced effect after dialysis is referred to as ‘hangover’. The current dialysis methods achieve only about 10 to 20% overall clearance as compared to a healthy kidney with filtering generally being inadequate. Because of the difficulty to control liquid levels in dialysis patients there are usually large fluctuations. Kidney and dialysis patients therefore are bound to a very strict drinking and diet regime. Another difficulty is that only the extra cellular liquid of a patient can be subjected to a dialysis treatment. All intra cellular amounts of liquid can only indirectly and gradually become part of a dialysis treatment, but are not instantly treatable. Basically the currently practised forms of dialysis only offer a life-saving treatment. The patient's health status during dialysis is usually poor, because the available renal replacement treatments can at best only provide relief for part of the failing renal functions. While endocrine and homeostatic functions can be performed to a reasonable extent, the excretion of organic anions and cations, and of protein-bound middle molecules cannot be replaced by the currently performed therapies. Kidney transplantation has also been practised as a solution for patients with a permanent renal failure. Although such transplantations have often successfully restored renal functions in kidney patients, the health benefits have remained limited by the adverse effects of the necessary immunosuppressive therapy. Kidney transplantations are subject to the availability of transplantable kidneys and occasionally initially successful transplants have also failed in the course of time. Accordingly there still is a demand for more continuous forms of blood purification that include regulated excretion of excess fluid, electrolytes and uremic toxins. There thus also is a continued need for artificial kidney devices performing such purification that, at least, can be put on a table top, are wearable extracorporal by the patient in comfort or, better still, can be brought into an implantable form.